Problem: Simplify the following expression: $z = \dfrac{2r + 9}{r} \div \dfrac{1}{8}$
Dividing by a number is the same as multiplying by its inverse. $z = \dfrac{2r + 9}{r} \times \dfrac{8}{1}$ When multiplying fractions, we multiply the numerators and the denominators. $z = \dfrac{(2r + 9) \times 8} {(r) \times 1}$ $z = \dfrac{16r + 72}{r}$